Seems to work nicely, i really like that there is a setting for Size and trail. However there always seems to be some trail effect, i kinda like it thou and maybe it would look weird without it?
Tinkered around with the settings trying to get it right and found that something like this works.
Shape Solid, Size and Trail minimum and Filter to about 90%.
RGB 255 0 0 A 90
Settings in OBS 0.657 i had the Opacity 100 and Color Key (black) with similarity and Blend 25
EDIT: Could have actually read the guide you guys did 🙂 If you run it as Window capture as i did you got to mess around with the opacity and blend stuff to not get a blackish shadow in the trail. Running it as a game-capture the transparency setting in the Gaze Overlay works allot better.